Currently, discussions are underway within the Institute of Electrical and Electronics Engineers (“IEEE”) to determine a new Advanced Air Interface standard for broadband communication, denoted as 802.16m. One of the issues to be addressed under 802.16m is the use of relay stations (“RS”) in wireless communication systems.
Signal quality deterioration, temporary disruptions and even call drop off can happen when a mobile communication device or mobile station (“MS”) moves from a cell or area covered by one base station (“BS”) to a cell covered by a different BS. When relays are introduced to the system to increase coverage, at the cell edge there is still a need to handover from one BS to another. Handovers may even occur from one RS, i.e. RS1, connected to a first BS, i.e. BS1, to another RS2 connected to BS2. This additional process may cause additional delays increasing the severity of the service interruptions mentioned above. Certain RSs may be shared among multiple BSs, i.e. the RS may be able to communicate with two BSs in the same frame or same time.
Soft handoff and fast cell switching techniques have been proposed for handoffs in the past. However, soft handoffs require additional resources and experience prohibitive inter-BS coordination. Due to these challenges, not even Worldwide Interoperability for Microwave Access (“WiMAX”) products designed to operate according to IEEE standard 802.16e have implemented soft handoffs. Additionally, fast cell switching needs extra coordination among BSs. Currently there is no method included in the 802.16 standard to do fast cell switching between two relays because of the complexity involved.
Additionally, no provisions are defined which would allow the use of an RS as an interface translator, such as using 802.16 as a backhaul for providing a connection between any other networks, such as those networks operating under IEEE standards 802.11, 802.15 and 802.16.
Additionally, during disaster situations when a base station is disconnected from the network, there is no way for the BS to quickly, but temporarily, reestablish the essential communications through another BS. The repairs to backhaul can take several days to weeks of service interruption in a disaster situation.
Finally, when multiple carriers are used, the current 802.16j standard has a frame structure that supports communication from the BS to MSs and to the RS at the same time using the same frequency, f1, and from the RS to its MSs and to a second hop RS using a second frequency, f2. However, the reception at the relay from the BS at f1 and the transmission from relay to its MSs and subordinate RSs are at different times per the current frame structure, which effectively doubles the amount of resources required to transmit a message.
Therefore, there is a need for a wireless relay frame structure, protocol and operational functions which address the above deficiencies for use in IEEE standard 802.16m communications.